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Correct Answer: Option D — Sirius. Sirius is correct because it is it is about 8.6 light-years from Earth. It is also associated with a binary star system. Together, these two facts identify Sirius precisely within Universe. Why the other options are incorrect: Option A — Proxima Centauri: Proxima Centauri is it is about 4.24 light-years away. It is also associated with a red dwarf star, so these facts identify Proxima Centauri rather than Sirius. Option B — Polaris: Polaris is it lies close to the north celestial pole. It is also associated with a Cepheid variable star, so these facts identify Polaris rather than Sirius. Option C — Betelgeuse: Betelgeuse is it is a variable star nearing a late evolutionary stage. It is also associated with a red supergiant star, so these facts identify Betelgeuse rather than Sirius. Exam Takeaway: Link Sirius with “it is about 8.6 light-years from Earth” and “a binary star system” for quick revision.
